The present invention relates to metalworking operations such as the cold rolling and hot rolling of aluminum and aluminum alloys. More particularly, the invention relates to an aqueous synthetic lubricant composition for use in such metalworking operations.
In the rolling of metals such as aluminum and aluminum alloys, it is customary to flood the rolls and the workpiece with a coolant for the purpose of carrying away heat generated by the operation. It is also customary to employ the coolant in combination with various agents having load bearing and friction-modifying properties for reducing friction between the rolls and the workpiece. It has heretofore been the practice to use for such purpose aqueous compositions containing such lubricating agents as emulsified petroleum and non-petroleum additives. In order to perform satisfactorily on an industrial scale, an aqueous lubricant fluid must meet several important requirements.
Among the requirements for a satisfactory metalworking lubricant are corrosion-inhibiting properties and stability under conditions of operation. While various fluids may possess such characteristics, there are also other important requirements that should be met. Among these requirements is the avoidance of deposits on the rolls and workpiece following the rolling operation. Such deposits result from drying of the fluid, and they are difficult to remove. Other important requirements include avoidance of excessive foam formation. Metalworking lubricants in the form of aqueous solutions have generally not been able to satisfy all of the foregoing requirements prior to the present invention.
Metalworking methods using single phase aqueous lubricant compositions are known in the prior art. However, prior to the present invention, metalworking with single phase aqueous lubricant compositions was not in widespread commercial use because of the inability of such compositions to satisfy simultaneously each of the requirements listed above.
Beaubien et al. U.S. Pat. No. 2,825,693 claims a metalworking lubricant concentrate comprising about 5-20% each of a block polyoxypropylene-polyoxyethylene copolymer and a random polyoxypropylene-polyoxyethylene copolymer, about 1-12% each of sodium nitrite and ethanolamine, and about 0.01-5% of an unsaturated high molecular weight fatty acid. The block polyoxypropylene-polyoxyethylene copolymers disclosed by Beaubien et al. are not conjugated in the order polyoxypropylene-polyoxyethylene-polyoxypropylene, as claimed in the present invention.
Reamer U.S. Pat. No. 2,981,686 discloses an aqueous metalworking lubricant comprising a water-soluble hetero-copolymer of a mixture of oxyethylene and oxypropylene groups. The Reamer patent states that block copolymers of ethylene oxide and propylene oxide are undesirable in such lubricants because of the tendency of these copolymers to produce "undesirable frictional problems, foaming, instability and the like".
Davis U.S. Pat. No. 3,374,171 claims a cutting fluid containing about 5-40% of a water-soluble alkanolamine, about 0.9-9% of a saturated organic acid having about 6-9 carbon atoms per molecule, and about 0.5-20% of a water-soluble polyoxyalkylene glycol. The Davis patent contains no specific teaching of the utility of polyoxyethylene-polyoxypropylene-polyoxyethylene block copolymers as ingredients of aqueous metalworking compositions. In addition, Davis cautions against the use of higher molecular weight saturated organic acids. He states that such higher organic acids can result in poor hard water stability, reduced corrosion-inhibiting properties and high foaming tendencies. These problems are said to lead to clogged filters, poor rust protection and reduced tool life in areas where hard water is encountered.
Felton U.S. Pat. No. 4,033,886 discloses a liquid suitable for the formation of a recyclable metalworking lubricant. The liquid is an aqueous solution containing a mixture of ethylene oxide-propylene oxide block copolymers, an alkanolamine cinnamate and a boron amine complex. The block copolymers have a central portion of polypropylene oxide with polyethylene oxide on each end (see column 2, lines 32-33).
It is a principal object of the present invention to provide a metalworking method employing a lubricant composition having acceptable load bearing and friction-modifying properties, corrosion-inhibition ability and chemical stability under ordinary operating conditions, and avoidance of deposits on tools and workpieces following operations in which the lubricant composition is used.
It is a related object of the invention to provide a lubricant composition accomplishing the foregoing objectives while at the same time avoiding excessive production of foam.
Additional objects and advantages of the present invention will become apparent to persons skilled in the art from the following specification.